Control circuit for vapor electric discharge devices



July 12, 1932. w, COCKRELL 1,867,398

CONTROL CIRCUIT FOR VAPOR ELECTRIC DISCHARGE DEVICES Filed Oct. 28. 1951 Irwvem tor William D. Cockr el I,

H is Attorney- Patented July 12, 1932 UNITED STATES PATENT MCE WILLIAM D. COCKRELL, F SGHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELEG- TRIO COMPANY, A CORPORATION 015 NEW YORK CONTROL CIRCUIT FOR VAPOR EIiEC'TBIG DISCHARGE DEVICES Application filed October as, 1931. Serial It'o. 571,694..

I effected by a photo-electric device operating through an electron discharge device. It 1s the object of my invention to provide an imroved circuit of this character which 1s adapted for high speed operation, is simple in form, and is economical and efiicient in operation.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. 1

In the single figure of the drawing which is a circuit diagram illustrating one embodiment of my invention I have shownat 1 and 2 the negative and positive sides respectively of a direct current supply circuit. Extending across this circuit is the voltage divider comprising resistance 3, potentiometer 4:, and resistance 5. At 6 I have represented a vapor electric discharge device, having an anode 7, cathode 8, a grid 9 and a cathode heater 10. The device 6 is connected in series with a load device, such for example as the relay 12, between the positive side 2 of the supply circuit and the point 13 on the voltage divider between resistance 3 and potentiometer 4:. Inasmuch as the vapor electric device 6, being operated on a direct current circuit, will continue to pass current after once being gr started independently of the grid, it is necessary to provide some means to open the plate circuit. For this purpose I have shown in the present case a rotatable circuit opening device 14 which at each revolution will open the plate circuit. The opening device 14 may be driven by any suitable means such as the apparatus or machine which the relay is arrangedto control. It will be understood, however, that any other suitable means may be employed for opening the plate circuit. In the apparatus illustrated the cathode heater 10 is shown connected through the transformer 15 with the alternatin current heat- 1ng circuit 16. The anode is connected through the relay 12 and circuit opener 14 with the positive side of the sup ly circuit, and the cathode 8 is connected wi h the volt age dlvider at the point 13 whereby the anode is always positive with respect to the cathode. The grid 9 is connected by the conductor 18 through the protective resistance 19 and the resistance 20 with the adjustable arm 21 of the potentiometer 4: which arm it will be noted is on the negative side of the point 13. For controllin the vapor discharge device 6 I have shown t e photo-electric tube 23 which efl'ects its control through the electron discharge device 24. Across the supply circuit 1, 2 is a second voltage divider comprising the resistances 25 and 26 and in shunt with the resistance 25 is the branch circuit comprising the high resistance 27 and the hoto-electric device 23 arranged in series. '1 e cathode 28 of the electron discharge device 24 is arranged to be heated by a connection including the transformer 29 with the alternatin current heating circuit 16, and by means 0 the conductor 30 between the midpoint of the secondary windin of transformer 29 and the conductor 18 t e cathode is connected with the circuit of grid 9 of device 6. Anode 31 of device 24 connects directly with the positive side of the direct current source and id 32 connects by conductor 33 with the photo-electric device 23 and resistance 27.

In the operation of the apparatus, when the photo-electric device is not subjected to ,serees light the potential of the grid 32 is suificiently usual manner by rendering its grid positive with respect to its cathode. The resulting current flow through device 24, resistances 20 and 5, and that part of resistance 4 included in the circuit, produces a potential drop across those resistances such that the grid 9 of the Vapor device 6 becomes positive with respect to the cathode 8. Device 6 thereupon begins to pass current causing the relay 12 to close and will continue to pass current until the circuit opening device 14 rotates to the point at which it opens the circuit. The negative bias applied to the grid of the vapor device 6 and the discharge current of the device 24 necessary to tripthe device 6 may be varied by the adjustment of the potentiometer arm 21. It will be noted that by connecting the photo-electric device 23 with a separate voltage .divider rather than with the divider comprising resistances 3, 4, and 5, the device is protected against the application of an over-voltage, for if device 23 were to be connected to the other voltage divider it will be seen that when the vapor electric device 6 began conducting it would magnify the voltage drops across resistances'4 and 5 and the device might thereby be subjected to a dangerously high voltage. It will also be seen that when the vapor device 6 begins to conduct, the cathode 28 of device 24 becomes much more positive which in effect renders the grid 32 strongly negative thus cutting off the flow of current through device 24 and producing a more economical operation of this part of the apparatus. It is true that as soon as device 24 beings to pass current its'cathode is rendered more positive by reason of the potential drop through resistances 20, 5, and a portion of resistance 4 which means that both the effective plate voltage is decreased and the negative grid bias is increased, both of which factors cause the plate current to decrease and thus have a compensating effect. This apparent lack in sensitivity, however, is not serious in most applications where there is an abundance of light for the operationof the photo-electric device. It will also be noted that with the above described arrangement the vapor electric device 6 is held inoperative not by reason of the operation of the device 24 but by reason of its grid connection with-the voltage divider; hence if device 24 for any reason becomes inoperative or defective the vapor electric device 6 remains inoperative to pass current.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a direct current supply circuit, a vapor electric device having anode and cathode elements connected therewith and having a grid, means for supplyin to said grid from said circuit a potential w ich is negative with respect to that of said cathode and a control device for supplying to said grid from said jcircuit a potential which is positive with respect to that of the cathode.

2. In combination, a direct current supply circuit, a vapor electric device connected therewith having anode, cathode and grid elements, a resistance between said cathode and the negative side of said circuit, means connecting said grid with an intermediate point of said resistance and an electron discharge device connected between the positive side of said circuit and said grid for reversing the relative polarity of the grid and cathode of said vapor device.

3. In combination, a direct current supply circuit, a voltage divider across said circuit, a vapor electric device having an anode con nected with the positive side of the circuit, a cathode connected with an intermediate point of said divider and a grid connected with the divider between the negative side of the circuit and said intermediate point, an electron discharge device connected between the positive side of said circuit and said grid for giving the grid a potential positive with respect to the cathode.

4. In combination, a direct current supply circuit, a vapor electric device and a resistance connected in series across said circuit, a controlling electron discharge device for said vapor device having anode, cathode and grid elements, means connecting said cathode with an intermediate point of said resistance, and means independent of said resistance for supplying a variable potential to said grid,

whereby when the vapor device becomes conducting the resulting potential drop in said resistance raises the potential of the cathode above that of the grid.

5. In combination, a direct current supply circuit, a voltage divider across said circuit, a vapor electric device connected between one side of said circuit and an intermediate point of said divider, a second voltage divider across said circuit and control means for said vapor device including a photo-electric device connected with said second divider.

6. In combination, a direct current supply circuit, a vapor electric device having an anode, a cathode and a grid, a load device connected between the anode and the posi tive side of said circuit, a voltage divider connected across said circuit, a connection between said cathode and an intermediate point of said divider, an electron discharge device having an anode, a cathode and a grid, said anode being connected with the positive side of said circuit, and said cathode being connected with the grid of said vapor device and with said divider at a point between the negative side of said circuit and said intermediate point, a second voltage divider across said circuit, a photo-electric device and a resistance arranged in series forming a branch connected between the negative-slde of said- 1 circuit and an intermediate point of the sec- 0nd divider, the grid of said discharge device being connected with said branch between the photo-electric device and the resistance.

In witness whereof, I have hereunto set my hand. v

- WILLIAM D. COCKRELL. 

